> CAT /RESEARCH/TB-500.DAT
TB-500 (Ac-LKKTETQ): Thirty Years of Thymosin Beta-4 Fragment Research, Dumped From the Peer-Reviewed Record
Seven residues. Forty-three amino acids in the parent protein. Eighteen published studies on the literature console. Every finding tagged by evidence class — [PRECLINICAL], [HUMAN], [WARN] — and cited.
What Is TB-500?
TB-500 is a synthetic heptapeptide — seven amino acids, sequence Ac-LKKTETQ — corresponding to residues 17-23 of the endogenous 43-amino-acid protein thymosin beta-4. Molecular weight: 801.9 Da. The fragment retains the actin-binding domain of the parent protein and has been the subject of tissue-repair and inflammation-modulation studies primarily in rodent and equine models.
Thymosin beta-4 is the primary actin-sequestering molecule in mammalian cells. It suppresses inflammatory chemokines and cytokines while promoting cell migration, angiogenesis, and stem cell maturation across multiple animal models [1]. TB-500 is the synthetic derivative of its active core region, studied as a research tool for understanding the parent protein's wound-healing, anti-inflammatory, and cardioprotective properties.
No randomized controlled human trial has been published using the TB-500 heptapeptide specifically. Phase 1 studies have been completed for full-length thymosin beta-4 [9] [12], and Phase 2 topical studies enrolled patients with venous and pressure ulcers [6] [7], demonstrating a safety profile and wound-healing signal. The fragment record is almost entirely preclinical.
TB-500 is not FDA-approved for any human indication. It is prohibited by the World Anti-Doping Agency under the Prohibited List (S0 and S2 categories) [8]. It exists in a regulatory gray area as an unapproved research chemical in the United States.
What Is TB-500 Used For in Research?
Research applications span five tissue domains: soft-tissue repair (tendon, ligament, dermal wound), corneal wound healing, cardiac ischemia protection, bone healing, and hair follicle activation. All studied primarily in rodent models, with some equine data and limited human Phase 1-2 data from the full-length parent protein.
The most extensively studied application is soft-tissue repair. Thymosin beta-4 applied to transected rat medial collateral ligaments produced significantly improved mechanical properties at four weeks — uniform, evenly spaced collagen fibers with larger fibril diameters and higher femur-ligament-tibia complex strength compared to controls [3]. Incisional wound models in rats showed superior collagen organization, reduced myofibroblast accumulation, and minimal scarring [4].
Cardiac protection is the research area with the strongest human evidence base, though this comes from full-length thymosin beta-4 rather than TB-500. Thymosin beta-4 reduced infarct size and improved cardiac function in mouse coronary artery ligation models [5]. Human Phase 1 studies of recombinant thymosin beta-4 confirmed safety and dose-proportional pharmacokinetics [9] [12], with sustained-release scaffold delivery continuing as a research frontier [15].
For TB-500 dosage protocols in research and for TB-500 side effects, dedicated pages compile the relevant preclinical and equine data.
What Are the Benefits of TB-500 Peptide in Research Models?
Preclinical data documents several reproduced outcomes across tissue-repair models. The strongest quantitative signals:
Wound healing. Intradermal thymosin beta-4 twice weekly improved wound closure, granulation, and vascularization in diabetic mouse burn wound models and reduced expression of RAGE (Receptor for Advanced Glycation End Products), a primary driver of impaired healing in diabetic tissue [10]. A 2024 controlled rat model confirmed multi-mechanism wound acceleration: measurable angiogenesis at day 3, enhanced new epithelial thickness throughout the healing timeline [13].
Inflammation reduction. Thymosin beta-4 inhibited TNF-alpha-induced NF-kB RelA/p65 nuclear translocation and downstream IL-8 expression in human corneal epithelial cells — an anti-inflammatory effect operating independently of the peptide's actin-binding function [14]. Rat post-extraction socket models showed reduced apoptosis and inflammatory infiltrate with enhanced granulation and new bone formation [11].
Hair follicle activation. Transgenic mice overexpressing thymosin beta-4 showed faster depilation-triggered hair regrowth; knockout mice displayed delayed regrowth — demonstrating a dose-dependent role for the protein in the anagen (active growth) phase [11]. Elevated VEGF and MMP-2 expression and activated P38/ERK/AKT signaling were identified as the downstream mechanisms [11].
Cardiac protection. Mouse coronary artery ligation models: reduced infarct size, enhanced early cardiomyocyte survival, improved cardiac function — via the PINCH-ILK-Akt pathway [5].
All of the above outcomes were observed in animal models or in vitro. No controlled human trial of the TB-500 heptapeptide specifically has been published.
State of the Evidence: TB-500 Research Summary
The evidence base is stratified by evidence class:
[PRECLINICAL] Rodent in vitro and in vivo: primary source of mechanism data and tissue-repair outcomes. Cell migration, actin sequestration, NF-kB inhibition, angiogenesis promotion, and cardiac infarct reduction are all preclinical findings.
[PRECLINICAL] Equine: anti-doping detection validated in horse plasma and urine by WADA-accredited LC-MS/MS, with detection limits of 0.02 ng/mL in equine plasma and 0.01 ng/mL in equine urine [8]. Doping violations in equestrian sport provide the most prominent real-world regulatory record for TB-500.
[HUMAN] Full-length thymosin beta-4 (43-amino-acid parent protein, not the 7-residue fragment): Phase 1 IV safety study in healthy volunteers confirmed no dose-limiting toxicity across four ascending dose cohorts (42-1260 mg) and dose-proportional pharmacokinetics [9]. First-in-human Phase 1 of recombinant Tβ4 in 84 Chinese volunteers (0.05-25.0 ug/kg) confirmed well-tolerated pharmacokinetics with no accumulation [12]. Phase 2 topical venous ulcer studies showed safety and a wound healing signal [6] [7].
[WARN] Fragment vs. parent disambiguation: most mechanistic and therapeutic data are derived from studies using full-length thymosin beta-4 (43 amino acids). Direct extrapolation to the 7-residue TB-500 fragment requires caution. A 2024 study found the parent heptapeptide Ac-LKKTETQ may not itself be the primary active species — the metabolite Ac-LKKTE drove the observed wound healing effect.
For frequently asked questions about TB-500, see the FAQ page.